In recent years, line-of-sight detection technologies have been used in, for example, shops or digital signage as well as in a user interface of a personal computer to conduct research on a product or information that a customer has an interest in. For example, in a line-of-sight technology, an infrared image is captured that includes the head of a user onto which infrared light is radiated, so as to detect a line of sight of the user on the basis of a location of a corneal reflection and a location of a pupil in the infrared image.
In this type of line-of-sight detection technology, when a person whose line of sight is to be detected is wearing glasses, infrared light is reflected onto a lens of the glasses, and a reflection of infrared light that is different from a corneal reflection may be seen on a portion of the lens of the glasses in a captured image. This reflection of infrared light that is different from a corneal reflection may prevent an extraction of a corneal reflection.
As a method for preventing a reflection of infrared light onto a lens of glasses from appearing in an image, a method is known that includes arranging two sets of an infrared light source and an image-capturing device away from each other and changing the set to be used from one set to the other according to an orientation of the face of a person (see, for example, Document 1)
A method is known that distinguishes a corneal reflection from a reflection onto a lens of glasses by detecting, as a corneal reflection, a reflection that occurs intermittently using the fact that a corneal reflection does not appear in an image when the eyes are closed due to blinking (see, for example, Document 2).
Document 1: Japanese Laid-open Patent Publication No. 2006-167256
Document 2: Japanese Laid-open Patent Publication No. 2012-239550